A molecular dissection of caveolin-1 membrane attachment and oligomerization - Two separate regions of the caveolin-1 C-terminal domain mediate membrane binding and oligomer/oligomer interactions in vivo

Caveolins form interlocking networks on the cytoplasmic face of caveolae. T he cytoplasmically directed N and C termini of caveolins are separated by a central hydrophobic segment, which is believed to form a hairpin within th e membrane. Here, we report that the caveolin scaffolding domain (CSD, resi dues 82-101), and the C terminus (residues 135-178) of caveolin-1 are each sufficient to anchor green fluorescent protein (GFP) to membranes in vivo. We also show that the first 16 residues of the C terminus (i.e. residues 13 5-150) are necessary and sufficient to attach GFP to membranes. When fused to the caveolin-1 C terminus, GFP co-localizes with two trans-Golgi markers and is excluded from caveolae. In contrast, the CSD targets GFP to caveola e, albeit less efficiently than full-length caveolin-1. Thus, caveolin-1 co ntains at least two membrane attachment signals: the CSD, dictating caveola r localization, and the C terminus, driving trans-Golgi localization. Addit ionally, we find that caveolin-1 oligomer/oligomer interactions require the distal third of the caveolin-1 C terminus. Thus, the caveolin-1 C-terminal domain has two separate functions: (i) membrane attachment (proximal third ) and (ii) protein/protein interactions (distal third).